PROTEOLYTIC CLEAVAGE OF PSEUDOMONAS-AERUGINOSA EXOTOXIN-A IN THE PRESENCE OF LIPID BILAYERS OF DIFFERENT COMPOSITION

Pseudomonas aeruginosa exotoxin A (ETA) must be proteolytically nicked by furin at Arg(279) before being translocated into the cytosol of ta rget cells. A similar cleavage can also be obtained with trypsin. Usin g this assay we could show that the interaction with lipid bilayers ca n strongly influence the extent of nicking. We found that in the prese nce of vesicles containing negatively charged lipids ETA is cleaved in to its two fragments A and B at enzyme concentrations similar to 50 ti mes lower, or at pH values higher by 1.5 units, than in the absence of lipids. We suggest that the interaction with the lipid bilayer of the positively charged loop containing Arg(279) provides the energy for i ts partial unfolding and makes it more accessible for proteolysis. (C) 1998 Federation of European Biochemical Societies.